This skill will increase the chance of your rift entity informing you when a spell effect or stun drops from it. It may also help retain control for longer periods of time. Train this skill, but not at the expense of your other abilities.
The in game help reads:
Skill duration: random. Type of skill : automatic skill (arcane skill). Affecting stats: None. It uses no endurance points. A skilled riftwalker must know how to control his entity, and this skill will assist him/her in a variety of spells. Amongst other things, this skill will help a riftwalker to sense if a spell effect drops from his entity.